The present invention relates to an apparatus for and method of evenly distributing the electrical load in a three phase electrical power distribution network.
Presently, many residential homes and commercial facilities receive, at their service entrances, all three phases in a three phase electrical power distribution network provided by an electric utility or power company. In a typical three phase distribution environment each phase supplies one or more branch circuits. The determination of which branch circuit or circuits to wire to each of the three incoming phases is usually made at the time the facility is designed or constructed and is difficult to change once the facility is completed. For example, in a residential facility, different branch circuits might supply the kitchen, living room, bedrooms, etc. with electricity. In a commercial environment, different branch circuits might supply machinery, offices, etc. A problem that arises frequently is how to evenly distribute electrical power across from the three incoming phases, supplied by the electric utility, to all branch circuits. Often, over time, the load topology of a facility will change, sometimes drastically. Some branch circuits become more heavily loaded and others less heavily loaded, due to, for example, movement of machinery on a factory floor, the addition of or movement of high wattage appliances (i.e. refrigerator, electric stove, microwave oven, etc.) in a home. Thus, the load on each of the three incoming phases will also change with the changing load on the branch circuits. A three phase network that was evenly balanced initially might become unbalanced over time.
One solution to this problem is to reassign each branch circuit to an incoming phase to achieve an even load across all three phases by physically rewiring each branch circuit. A disadvantage of this solution is that it potentially requires the costly rewiring of electrical closets and distribution panels every time the three phases become unbalanced, which might occur frequently. Another disadvantage is that the rewiring typically requires a disruption in power causing a potential problem for utility customers. In addition, this solution only provides a crude mechanism of balancing the load across the three incoming phases. It does not track power consumption on each phase and branch circuit on a frequent basis. The hour to hour and minute to minute changes in electrical loading that occur, which might be large enough to cause major unbalancing across the three incoming phases, pass undetected.